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From "Hyunsik Choi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (TAJO-391) Change setting default type in query from FLOAT4 to FLOAT8
Date Fri, 06 Dec 2013 17:23:35 GMT

    [ https://issues.apache.org/jira/browse/TAJO-391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13841444#comment-13841444
] 

Hyunsik Choi commented on TAJO-391:
-----------------------------------

This proposal is reasonable for me. I have also experienced the problem caused by downcast.
The function type system works well when column references are passed to functions. However,
it is likely to lose precision when constant values are used as function parameters. This
is because real values are parsed via FLOAT4. This change only affects function call with
constant parameters, so it does not cause performance degrade.

> Change setting default type in query from FLOAT4 to FLOAT8
> ----------------------------------------------------------
>
>                 Key: TAJO-391
>                 URL: https://issues.apache.org/jira/browse/TAJO-391
>             Project: Tajo
>          Issue Type: Improvement
>          Components: operator/function/udf
>            Reporter: DaeMyung Kang
>            Assignee: DaeMyung Kang
>            Priority: Minor
>             Fix For: 0.8-incubating
>
>         Attachments: TAJO-391.patch
>
>
> FLOAT4 is default parsed float type in tajo.
> but it can cause some trobles when we use it as FLOAT8.
> for examples.
> 0.4(f) will changed to 0.40000000000005(d)
> so it cause different result from java.Math functions.



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